CXX-2659 Add change_stream::next()#1594
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eramongodb merged 3 commits intomongodb:masterfrom Mar 12, 2026
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kevinAlbs
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Nice, LGTM with a rename to try_next.
kevinAlbs
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LGTM with a documentation tweak. I am very happy to see this simplify common use of the change stream API.
| /// | ||
| /// Try to obtain the next event document. | ||
| /// | ||
| /// This function does not block: the underlying cursor is advanced only once. |
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Advancing the cursor may block (for up to maxAwaitTimeMS). try_next gives users an option to exit early and/or save the current resume token.
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| /// This function does not block: the underlying cursor is advanced only once. | |
| /// This function does not block indefinitely: the underlying cursor is advanced only once. |
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Resolves CXX-2659 by exposing the
advance_iterator()internal helper as a public.next()function. As suggested by CXX-2659, the function returns the event document. However, rather than throwing an exception, the return value is made an optional instead, wherecs.next().has_value()is effectively equivalent to(++iter) != cs.end(). The existing change streams iteration test case is updated to reflect this equivalence betweencs.next()and++iter, including the fact that.next()followed by.begin()does not advance the underlying cursor (the reverse order is not true).